08-30-2012, 12:50 PM
[quote name='Frank' timestamp='1346296101' post='19881']
It is well known that in a Bayer sensor the number of green cells is twice the number of red/blue cells and it is said that this is because human eyes are more sensitive to green light. For "human eyes are more sensitive to green light", I interpret it as for the same amount of green light and red/blue light, the green light looks brighter, e.g., by a factor of k>1. If this is correct (indeed it is correct), then, suppose that we arrange a sensor to have the same number of green/red/blue cells, the cells have the same sensitivity to their colors, then for the same amount of green/red/blue light the censor of each color will record the same amount of light for each color. When this is converted to a RGB image properly, the amount of green/red/blue would still be the same. Then, because "human eyes are more sensitive to green light", when we look at this image we would still think that the green color is brighter than the red/blue color, by a factor of k. Based on this logic, I don't understand why a censor need to have twice number of green cells than the number of red/blue cells.
A similar question applys to conversion of a color image to a bw image: usually during the conversion more weight is given to the green light when calculating brightness (e.g., 60% green + 30% red + 10% blue). For a Bayer sensor more weight is already given to the green color (twice number of green cells). Is that weight still not enough for compensating the brightness difference?
Best regards,
Frank
[/quote]
to add a bit to what brightcolors said, first a link:
http://hyperphysics.phy-astr.gsu.edu/hba...e.html#c3b
If you look at this, you will see that e.g., blue cone density is much smaller. Furthermore, due to chromatic aberration, blue light is slightly out of focus in our eyes. If you have ever seen something that was only illuminated by dim pure blue light (neon), you will have noticed it looks blurry if no other cones or rods are triggered. So, our blue vision is rather unsharp. Therefore, theoretically, you don't need that many blue sensors, because we don't see that well in that light frequency.
It is well known that in a Bayer sensor the number of green cells is twice the number of red/blue cells and it is said that this is because human eyes are more sensitive to green light. For "human eyes are more sensitive to green light", I interpret it as for the same amount of green light and red/blue light, the green light looks brighter, e.g., by a factor of k>1. If this is correct (indeed it is correct), then, suppose that we arrange a sensor to have the same number of green/red/blue cells, the cells have the same sensitivity to their colors, then for the same amount of green/red/blue light the censor of each color will record the same amount of light for each color. When this is converted to a RGB image properly, the amount of green/red/blue would still be the same. Then, because "human eyes are more sensitive to green light", when we look at this image we would still think that the green color is brighter than the red/blue color, by a factor of k. Based on this logic, I don't understand why a censor need to have twice number of green cells than the number of red/blue cells.
A similar question applys to conversion of a color image to a bw image: usually during the conversion more weight is given to the green light when calculating brightness (e.g., 60% green + 30% red + 10% blue). For a Bayer sensor more weight is already given to the green color (twice number of green cells). Is that weight still not enough for compensating the brightness difference?
Best regards,
Frank
[/quote]
to add a bit to what brightcolors said, first a link:
http://hyperphysics.phy-astr.gsu.edu/hba...e.html#c3b
If you look at this, you will see that e.g., blue cone density is much smaller. Furthermore, due to chromatic aberration, blue light is slightly out of focus in our eyes. If you have ever seen something that was only illuminated by dim pure blue light (neon), you will have noticed it looks blurry if no other cones or rods are triggered. So, our blue vision is rather unsharp. Therefore, theoretically, you don't need that many blue sensors, because we don't see that well in that light frequency.